signature Icon is icluded into Artistic Toolbar Icons. You can view all business icons here:
These icons are delivered in sizes 16x16, 24x24, 32x32, 48x48 and also 256x256 used for Windows Vista. The icons come in two color variants: 256 colors and True Color with semi-transparency. They also have several file formats, such as ICO, PNG, GIF and BMP.
Download link: www.777icons.com/downloads/artistic-toolbar-icons.zip